Small engines having one or more cylinders and less than twenty-five horsepower are used in a wide variety of applications. These applications range from single cylinder lawn mowers to multi-cylinder engines used on garden implements, portable generators, and motorcycles. Other such engines are used to power refrigeration units for refrigerated transport vehicles such as tractor-trailers. Scooters mopeds, and other types of motorcycles that use this same type of small internal combustion engine are in worldwide use. There are several manufacturers of these smaller engines including, for example, Tecumseh Products Inc. and Briggs and Stratton Corporation, among others.
The standard fuel delivery system for such engines is currently a carburetor-based system. However, such carburetor-based systems are relatively fuel inefficient resulting in undesirable levels of emissions caused by engine operations that generate excess hydrocarbons and evaporative emissions. Additionally, carburetor-based systems usually require high maintenance and are difficult to adjust for maximum efficiency. Carburetor-based systems also can sometimes be very hard to start in certain conditions and are very difficult to operate without generation of high levels of unwanted fuel emissions. In some regions of the world, including some areas of the United States, there is a pressing need for a fuel delivery system that eliminates these unwanted fuel emissions and prevent the steady increase of air pollution in heavily populated areas.
To rectify some of the fundamental problems associated with carburetor-based fuel delivery systems, there have been attempts to design fuel management systems for smaller internal combustion engines. These attempts have usually been fuel injector-based systems. Most of these fuel injection systems are simply scaled down versions of standard automobile fuel injection systems. They normally operate at fuel pressures of about 30-90 psi. Therefore, these systems are usually cost prohibitive in applications of twenty five horse power and less. Fuel injection systems also not fuel efficient when used with internal combustion engines in that horse power range, and they usually require a large number of expensive and complex components. Fuel injection systems also require a significant amount of electrical energy to operate the components of the systems such as the high pressure fuel pumps. This higher electrical requirement requires a commensurate addition of electrical generating capacity as well as the inclusion of additional electrical generation components associated with such higher capacities. The addition of these electrical generation devices results in a notable reduction in the available horsepower generated by the engine.
To control the fuel delivery and fuel mixture in the previous known fuel injector-based fuel systems, various timing and sensing components must also be added to the engine. For example, toothed gears and other sensing devices for determination of the angle of either the crankshaft or the camshaft are used to ensure that fuel is delivered to a cylinder at just the appropriate time and in just the appropriate amount. These additional components increase the cost of fuel injector-based fuel delivery systems and add to the overall complexity of the systems.
Thus, while previous attempts to design a fuel injection delivery system may have overcome some of the problems associated with carburetor-based fuel delivery systems, current fuel injection systems do so at the cost of requiring a costly and complex system that contains a significant number of components that rob the internal combustion engine of significant amounts of available horsepower.
It is noted that U.S. Pat. No. 6,343,596 (the '596 patent) was issued to the current inventors and is incorporated herein by reference. The '596 patent disclosed and claimed an invention that was the starting point for the conception and development of the present invention. The present invention is a new and unique adaptation and improvement of the invention in the '596 patent. Specifically, the device in the '596 patent was a fuel regulator for use in two-cycle or four-cycle internal combustion engines. The system includes a microprocessor, a thermocouple exhaust gas temperature sensor, and a fuel regulating valve installed in a low-pressure fuel delivery system between the fuel tank and the carburetor. During operation, the microprocessor continually receives signals from the exhaust gas temperature sensor. These signals in the '596 patent are compared with stored temperature ranges to determine the optimum fuel mixture for the current engine operating conditions. If the current engine operating conditions require a variation in the fuel mixture setting, the microprocessor adjusts the degree of opening of the in-line fuel regulating value, and accordingly regulates the flow of fuel into the carburetor.
Like the device in the '596 patent, the present invention also includes a microprocessor and a fuel regulating valve installed in a low-pressure fuel delivery system between the fuel tank and the carburetor. However, unlike the device in the '596 patent, the current invention does not expressly require an exhaust gas temperature sensor, but uniquely involves sensors for air intake temperature, engine temperature, throttle position, and spark ignition to transmit signals to the microprocessor. Also, unlike the device in the '596 patent that uses the exhaust gas temperature as its baseline control input, the present invention uses the spark ignition signal as the baseline control input for fuel delivery operations within the microprocessor. The microprocessor of the current invention also employs a sophisticated method of controlling fuel delivery that includes, for example, comparing values determined by the signals transmitted from the spark ignition sensor, air intake temperature sensor, engine temperature sensor, and the throttle position sensor with values stored in various maps within the microprocessor. Based on the programming parameters of the present microprocessor, the fuel delivery system is continuously controlled and adjusted by the microprocessor to deliver fuel to increase overall engine operating efficiency.
Finally, because of the difference in size, complexity, and function of the larger engines on which the current invention is used, a number of improvements in and to some of the components generally disclosed in the '596 patent are made that allow those components to operate in a different manner to achieve the more sophisticated operational characteristics of the present invention. For example, the fuel pump, the fuel valve, and the throttle position switch of the present invention are new and novel components that have been especially designed to fulfill the objectives of the present application. Also, the level of complexity and sophistication of the microprocessor and the programs employed by it are significantly increased to accommodate the ability of the present invention to operate with greater efficiency when installed on larger sized two and four stroke internal combustion engines. Thus, while the device of the '596 patent meets the objectives as needed for the types engines considered in the '596 patent, the device herein includes a number of improvements and additional elements that distinguish it from the device in the '596 patent and allow the present device to operate more effectively with larger internal combustion engines such as those used in garden implements and motorcycles.